Friday, 18 November 2016

Chequamegon Ecosystem-Atmosphere Study (CHEAS)

Research Issue

We are collaborating with the National Oceanic and Atmospheric Administration (NOAA), University of Minnesota, University of Wisconsin, Pennsylvania State University, Carnegie Institute, and other participants in the Chequamegon Ecosystem-Atmosphere Study (ChEAS). The ChEAS is focused on understanding the processes controlling forest-atmosphere exchange of carbon dioxide, including carbon sequestration and ecosystem respiration, and the response of these processes to climate change and multiple environmental stresses.

Our Research

Our goal is to understand the dynamics of forest productivity in terms of net ecosystem exchange (NEE) for carbon dioxide (CO2) and create the knowledge base for CO2 fluxes in various forest types. The ChEAS consists of a cluster of eddy covariance towers for continuous monitoring of energy, water vapor, and CO2exchange between forest ecosystems and the atmosphere. Towers are located at various study sites in northern Wisconsin on the Chequamegon-Nicolet National Forest, where flux measurements are obtained at stand-level and landscape spatial scales. These towers are a part of the network of sites for studying energy, water, and carbon fluxes at the local, continental (AmeriFlux), and global (FluxNet) scales.

Our research unit participated in the NASA funded project, ‘Testing the Flux Tower Upscaling Hypothesis at a Regional Scale in a Complex Landscape’. In 2005 to 2007, we deployed two roving flux sensors to include unrepresented ecosystems, and add to the three permanent tower sites, namely, mature northern hardwoods, old-growth mixed forest, and alder-willow wetland. The four study sites for the roving eddy-covariance sensors included two recently harvested forest stands regenerating into 1) an aspen-dominated ecosystem, 2) a mixed aspen-red maple stand and two wetlands, 3) a sedge-grass-shrub fen, and 4) an ericaceous bog. These flux tower measurements in combination with biometric data and carbon stocks in dead, standing, and live biomass and soil carbon are integrated into the multi-tier studies of the North American Carbon Program (NACP). Flux tower data are also used to update the biogeochemical model, Biome-BGC, which we utilize for regional upscaling of carbon fluxes. Furthermore, we recently deployed an eddy-covariance tower (~ 15 m) in a 10-year old aspen stand, an ecosystem that has been unrepresented in the ChEAS stand-level measurements.

Expected Outcomes

Productivity and respiration maps of carbon fluxes according to forest types and age classes.

Landscape and regional upscaling on the impacts of elevated CO2 and O3 on carbon, water, and energy fluxes in aspen forests.

Testing the flux tower upscaling hypothesis in a complex landscape in northern Wisconsin.

Modeling complex ecosystems in support of the NACP Mid-Continent Intensive.

Upscaling carbon fluxes from stand-level towers to the footprint of a very tall tower in a heterogeneous landscape.

Research Results

Carbon fluxes obtained from the very tall landscape-level tower (400m, WLEF near Park Falls, WI) indicate that the landscape is a weak net source of CO2, yet stand-level towers in individual ecosystems within the landscape are net CO2 sinks. Fluxes measured from this tower will be used to link and upscale the results from the Aspen FACE experiment, where scientists are studying the effects of anticipated climate change (elevated CO2 and O3) on northern forest ecosystems.